In conventional radio receivers an oscillator circuit with a phase-locked control loop (PLL) which also includes an analog loop filter is used as a mixer oscillator. If a listener requires a change in the reception frequency of a radio receiver then, among other steps, the capacitors in the analog loop filter of the PLL must be recharged. The required recharging time causes the retuning of the radio receiver to seem slow, particularly during the switch-on of alternative frequencies during testing.
A mixer oscillator circuit with reduced a test time is described in German Application No. 145.102207.